Chem 112 Lab Final Experiment 10

Front 1

the unknown compound could have been

Back 1

glucose, sucrose, or glycerol

Front 2

learning objectives (4)

Back 2

calculate the molar mass of a dissolved compound using the experimentally observed freezing point depression

identify compounds based upon molar mass and physical properties

add linear trend lines to plotted data

graphically identify freezing points using linear extrapolation

Front 3

experimental objectives (2)

Back 3

determining the mass of a substance by difference

measuring the freezing points of pure solvents and solutions

Front 4

two cold-tolerant fish

Back 4

Atlantic Wolffish, Anarhichas lupus

rainbow smelt, Osmerus mordax

Front 5

what bug species survive freezing in north america

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beetles, Cucujus clavipes

eggs of locusts, Locusta migratoria

Front 6

what can survive being frozen solid

Back 6

terrestrial wood frog, Rana sylvatica

Front 7

in the _____, _______, a bio grad student, was researching how ______, a group of ____ species that live around ______, survived

Back 7

1960s

Arthur DeVries

notothenioids

fish

Antarctica

Front 8

how did the notothenioids survive

Back 8

they were expressing antifreeze proteins (AFPs)

Front 9

how to AFPs prevent the formation of big ice crystals in the cell

Back 9

they bind to small ice crystals, altering the structure of the crystal and prohibiting further growth

Front 10

are AFPs exclusive to notothenioids

Back 10

no, other fish and insect species also express AFPs

Front 11

how do cold-tolerant species lower the freezing point of water in their bodies

Back 11

they increase the concentration of dissolved solutes like sugars and glycerol in their tissues/blood plasma

Front 12

how does the terrestrial frog survive freezing

Back 12

it loses cellular water and converts glycogen to glucose within the cell

Front 13

freezing point depression is an example of a

Back 13

colligative property

Front 14

a physical property of solutions that depends on the number of dissolved particles in solution, but not the identity of the solute

Back 14

colligative property

Front 15

3 more colligative properties

Back 15

boiling point elevation, vapor pressure lowering, osmotic pressure

Front 16

for reasonable dilute solutions, colligative properties are entirely traceable to

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entropy

Front 17

second law of thermodynamics

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any spontaneous change occurs with an increase in the entropy of the universe

Front 18

a spontaneous change is a change that occurs with

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no outside intervention

Front 19

the universe is defined as

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the system and its surroundings

Front 20

deltaS_univ =

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deltaS_sys + deltaS_surr

Front 21

two related concepts associated with entropy function are

Back 21

disorder and probability

Front 22

freezing can only occur if deltaS_surr is

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positive and larger in magnitude than the negative deltaS_sys

Front 23

the universe tends to change in ways that have

Back 23

maximum probability

Front 24

solute molecules in a solution have the tendency to

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spread themselves evenly over the volume of the solution

Front 25

at the freezing point, the entropy gain of the surroundings is

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equal to the entropy loss of the solvent that freezes out

Front 26

transfer of heat (q) is always accompanied by

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an increase in entropy

Front 27

the lower the temp of the surroundings into which heat is released,

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the greater the entropy increase is

Front 28

deltaS_surr =

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q/T_surr

Front 29

the entropy change for the universe can be expressed as

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deltaS_sys + q/T_surr =deltaS_univ

Front 30

above the freezing point, entropy is

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less than zero

Front 31

at the freezing point, entropy is

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equal to -q/T_surr

Front 32

below the freezing point, entropy is

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greater than zero

Front 33

when the liquid A solute molecules start to freeze and the solute B becomes more concentrated, the entropy of B

Back 33

decreases

Front 34

when solid A freezes out of a solution containing some dissolved B, the entropy decrease is a bit _____ than when A freezes out from pure liquid A

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greater

Front 35

a lower temp is required for a solution because the entropy increase of the surroundings needs to

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balance the entropy decrease of the freezing of the liquid

Front 36

at the freezing point of a SOLUTION, the entropy change of the solution is equal to

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-q/T_surr

Front 37

the freezing point of the solution is ________ until all of the solvent is frozen

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further depressed

Front 38

deltaT_f =

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T_f pure solvent - T f solution

Front 39

the magnitude of deltaT_f is directly proportional to

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the concentration of the solute

Front 40

deltaT_f = (2nd equation)

Back 40

K_fm

Front 41

K_f

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the solvent-specific molar freezing depression constant

Front 42

m

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molality of the solution

Front 43

molal freezing point depression constant for water

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-1.8*C/m

Front 44

molality

Back 44

moles solute/kg solvent

Front 45

solutes that dissociate or ionize when dissolved in water

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electrolytes

Front 46

for ____, the number of moles of particles per formula unit in solution is greater than for _____

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electrolytes
nonelectrolytes

Front 47

the effective molality of a dissolved sodium chloride solution is ______ the calculated molality

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twice

Front 48

the freezing point for a solution will decrease until the _______ for the solvent is reached

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saturation point

Front 49

a solution has reached its saturation point when

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the solvent cannot dissolve additional solute

Front 50

for a solution being frozen, once the saturation point is reached, additional freezing

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forces solute out of solution, maintaining a constant molality for the solution

Front 51

the temp at which the solution becomes saturated

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eutectic temperature

Front 52

what is it called when the temp of the solution is lower than the eutectic temp without further precipitating solute from solution

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a supersaturated solution

Front 53

supercooled solutions can be prepared by

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carefully lowering the temp of the solution without agitation

Front 54

when disturbed, supercooled solutions can

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suddenly precipitate their solutes, forming saturated solutions

Front 55

during the precipitation of solute from a supercooled solution,

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heat is evolved, raising the temp of the solution back to the eutectic temp

Front 56

what other chemical did we use

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sodium chloride

Front 57

was special chemical waste collection required

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no

Front 58

how do you find the freezing point on the graph

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add trendlines for cooling and freezing and it's where they intersect

Front 59

what are the series you use with the solution graph

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cooling 1, cooling 2, freezing

Front 60

what's the freezing point for the solution on the graph

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the intersection of cooling 2 and freezing

Front 61

where should excused absences be reported

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412 held

Front 62

eutectic temp is the

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lowest temp at which the solvent is still a liquid

Front 63

matts ta hours are

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1-2 wed
8-9 thurs
116 held